The present invention relates to three-dimensional model-making systems.
By way of background, attention is called to an ASME paper entitled "Computer-Aided Design of Curved Surfaces with Automatic Model Generation" (Staley et al.) which was presented on Mar. 25, 1980; the author R. B. Jerard is the present inventor and the machine shown in FIG. 12 of the paper is the sole contribution of the present inventor, but the mathematics therein is not. See, also, "Sculpting via Computer Optics," American Machinist, September 1979, pp. 79-82; "Cutting with Wire: Laser Technology," Inc., Catalog No. 75-76. Attention is also called to U.S. Pat. Nos. 1,903,518; 2,144,370; 2,396,852; 2,599,920; 2,688,904; 2,831,476; 2,896,605; 3,153,355; 3,155,087; 3,208,127; 3,299,877; 3,508,457; 3,525,324; 3,755,701; 3,831,576; 3,866,052; 3,932,923; 4,016,856; 4,178,670.
Not included in the art just made of record is a substantial amount of art in which an engine lathe is used in combination with a rotary cutting tool mounted on the lathe head stock to permit x-y movement and the indexing of a workpiece for fluting or grooving of that workpiece.
The problem of visualizing and describing solid shapes in three dimensions is common to many fields of art and science and can be a major obstacle in the creative process. Architects, engineers, mathematicians, and artists are often faced with the necessity of picturing some space or surface which they have conceived and then communicating it to others, usually before an adequate representation of that surface exists. These persons might be engaged in work in any number of areas from fluid dynamics to architecture, from flow modeling to design or human engineering. Therefore, the need exists for some means to speed the representation of these shapes in order to introduce modeling directly to the creative process.
Traditionally, three-dimensional forms have been described by a series of drawings-two dimensional projections of the body on a set of orthogonal planes passing through it. These representations are insufficient for a number of reasons. First, the drawings do not represent complex shapes well since it is often difficult or impossible to show hidden features. Second, if all the details of a complex body were shown on a conventional sketch, the drawing would quickly become too cluttered to read. Third,two-dimensional representations of even simple objects are difficult to understand and often require long study by a practiced eye. Finally, drawings and sketches do not show the view how each projection of the body fits together. All of these drawbacks make it difficult for anyone to quickly and accurately describe an object in perspective based only on a set of drawings.
The design of three dimensional objects in a two dimensional medium has shaped products to a large extent. Many objects are designed a certain way simply because they can be drawn in plane views conveniently. Any experienced designer who has ever had to deal with a geometrically complicated design will testify to the truth of this statement. This limitation imposes an artificial constraint on the design which can result in either a poor design or expensive experimental iteration.
The use of computer graphics has been widely used to help augment the designers visualization abilities. Most systems for computer-aided design or manufacturing involve an extensive package of interactive graphics routines to allow designers to "speak" with it. This is usually done through a CRT screen or digitizing tablet which enables the operator to modify the design easily. In addition, these graphics systems often contain a sophisticated set of subprograms to allow the image to move or rotate to reveal hidden lines and new perspectives. The technique can become invaluable in understanding and analyzing an overall design from a set of simple 2-D projections.
Despite the increased utility the designer is still working in essentially a two dimensional medium. Visualization is aided by commercially available software routines which provide rotation, depth cueing, wiggle, and hidden line removal. In many cases these techniques may be more than adequate. However, a fast and convenient means of producing three dimensional models could often be a great aid.
Another important use of computer systems in industry is in computer aided manufacturing (CAM). These systems make use of the computer to guide a machine tool through a series of steps to produce some item or assembly. By combining this type of operation with a computer-aided design system, an integrated process is achieved with the potential to produce 3-D models quickly.
To produce a model using conventional numerical controlled (N/C) machining methods, the output of the designer is used by an N/C programmer to develop an APT (Automatic Programmed Tools) program for generating an N/C tape. This tape is then used to control a N/C machine tool to generate the model geometry defined by the APT program. The step involving the generation of N/C punched tape from an APT program is generally called post-processing. In the most general sense post-processing is taken to mean conversion of the mathematical description of a model geometry into control instructions for the machining of a three-dimensional object.
However, numerically controlled (NC) lathes and milling machines may be acceptable for the production area, but they are hardly fit for the design studio. Because of the materials and forces involved in these cutting processes, these machines are very large and heavy. In addition, the noise and debris produced by these machines make them unsuited to a creative environment. Finally, actual production-line equipment is very expensive and the cost of installing one of these to help the designer could probably not be justified. Another drawback associated with the NC approach is the extensive software required to determine the tool paths necessary to cut a given shape. For example, the software must take into account the diameter of the cutting tool and determine appropriate offsets. The designer requires a graphics system which is small and unobtrusive enough to be placed in his studio and which produces 3-D models from simple sketches and abstract shapes. To fit all of these requirements, a new generation of computer-controlled machines must be defined.
If the classical design cycle is contrasted with the design cycle suggested by the use of the present invention, there is a significant reduction in the number of steps, and therefore time, required to go from the initial rough sketch design to final model production. Since the designer sketches the design directly on the computer graphics screen and immediately constructs the mathematical model of the design geometry, it is not necessary for a draftsman to translate a sketch into a final detailed design drawing. Furthermore, since the output of the design session can be used without modification as input to the model generation facility, the N/C programmer is not required to generate an APT program from the detailed design drawings. This eliminates two often encountered sources of error in the classical design cycle: the interpretation of the design geometry into a sequence of machining operations, and the generation of an APT program to control a N/C machine tool.
It is a principal object of the present invention to provide a three-dimensional model-making system, one that permits facile translation of computer-designed shapes to three dimensional models.
Another object is to provide a system which is adapted to form such models from an easily-machinable material.
In order that a three-dimensional, model-making system form complex shapes in the time required by economics of the market place, and under computer control, it must be mobile and compact, it must cut rapidly but yet have a cutting mechanism with long life and that cutting mechanism must have sufficiently low inertia to permit rapid repositioning thereof. Still another object, therefore, is to provide a three-dimensional, model-making machine wherein the mechanical working parts of the machine are particularly well adapted to computer controls.
It is a further object to provide a way to free the designer from two dimensional design thinking with an easy and convenient mechanism for creating three dimensional physical models.
Another object of the invention is to develop a mechanical device which will easily interface with a computer graphics system to allow the designer to produce a three-dimensional model directly from a sketch, in his own studio.
Another object is to allow the designer to communicate shapes to others more easily than by drawings and to eliminate the costly and time-consuming process of hand-producing models.
A still further object is to generate models early in the design cycle thereby reducing the number of iterations required to produce a satisfactory design by exposing obvious errors during the initial phases of the design.
Still another objective is to move model creation from the shop into the design room, where it is visible and accessible to the designer.
It is another object of this work to create a 3-D model making machine that is inexpensive.
Another object is to create a machine easy to set up and simple enough to be operated by persons with no machining experience.
A further object is to present a machine that is compact and quiet enough to be used in the design room environment instead of the machine shop floor.
Another object is to permit creation of a 3-D model rapidly enough to allow its use in the preliminary design function.
Standard numerical control machines will produce models from computer generated tapes. But extensive post-processing of the part geometry must be done by NC languages such as APT. This complicated software slows the model making process and is a potential source of error. Therefore, it is still another object of this work to create a system simple enough to create models directly from the part geometry without extensive software.
Another objective of the device is to produce a system that is easily interfaced to a computer and that can be directly controlled by a large variety of digital computers. The machine should be configured as a computer peripheral.
These and still further objects are addressed hereafter.